Ultrastructural observations of small blood vessels in leprosy patients.

In lepromatous leprosy, blood vessels revealed the luminal protrusions of endothelial cells containing M. leprae and thickening of the basement membrane of endothelial and smooth cells. Endothelial projections with increased pinocytotic vesicles were more often encountered in lepromatous leprosy than in the other types of leprosy. On the other hand, in tuberculoid leprosy, the extensive rough endoplasmic reticulum suggesting protein synthesis was observed in the endothelial cells compared with the other types of leprosy and non-specific lesions. It seems that the blood vessels associated with hyperfunction and proliferation in the endothelium could aggravate the degenerative changes in peripheral nerve fibers including the Schwann cells.